What is your current topology? Core, distribution, access layer switches? When you say departments are they in the same building or over a WAN?

Our current topology is a mess. Our core and distribution is a mess of connections between switches. I would like to redo all of the interconnects between switches. All departments are in the same building. Basically each department has either a 2960 or 3560 switch. I was thinking of having 2 3560 handle all of the multicast routing and my 2960s just doing the IGMP snooping. I'm not 100% sure on how to interconnect all of these devices though and how I setup the load handling between 3560s or if that is even necessary. Thanks again!

well, i'm trying to understand the topology. What device is doing the inter vlan routing? which switches are connected to it? Is the inter vlan router the only switch layer 2? The only multicast configurations should be on the router. IP MULTICAST ROUTING, IP Pim spare-mode on the SVI's, and a RP on the router.

Right now everything is kind of connected to each other between devices. I'm pretty sure this is where most of our issues are stemming from. We have 2 3560's that are doing the inter Vlan routing right now. Would it be best to have only 1 3560 do all of the routing for the entire Vlan and have all other switches plugged into the 3560? All 3 of the 3560 are layer 3 I believe. One of my concerns is overloading any one switch with multicasts. That is why I was wondering if 2 3560s should be utilized as multicast routers with interconnects between them and then all other 2960s stem off of either 3560? Is this even possible? I'm not 100% sure what RPs do or how I need to set them up. Right now I have both 3560s setup to do the IP multicast routing in ip pim sparse-mode.

The real issue is weather or not your 3560's are capable of multicast routing. If you are running an IP BASE image then you will have to upgrade to Advanced IP services system image, which you'll need to purchase through Cisco. Run SHOW VERSION. The first line should give you the image. As for a RP, a Rendezvous Point is what it sounds like, a central meeting place for multicast source and receivers. You always want to configure the RP on the most centralized switch/router, such as the device doing your intervlan routing. If you say they are all in layer 3 that is fine, just configure it on the most centralized switch. You can just configure a loopback interface and use it's IP as the RP. You can configure IP PIM SPARSE-MODE and the SVI's you want to run multicast on.

When I originally got my 3560's they were running the BASE image and I have already purchased and upgraded all of them to be capable of doing the Advanced IP routing so I should be good there. Thanks for all of your help again! I understand the RP now but I have a few more questions. So am I going to setup multicast routing on all of my 3560's or just one and the rest like the 2960s? Do I need to specify in my 2960's where the multicast router is or will they automatically figure it out? Should I setup IGMP snooping on all of my switches? Is there any advantage to having more than one cable connecting all of my 2960s back to the central 3560? There is a thing called a smartport, should i use this for the ports where my 2960s connect back to the 3560? Thanks again you have been very helpful!

i believe so. i just have it on one core 4506 now. i would turn it on all of the 3560s and run PIM Sparse on all the SVI's. There should be only 1 RP though. IGMP snooping should be on all of them. I don't use smart ports although i have heard a lot of other people use them. i think they are just for access ports.

Thanks again! So I think I'm getting this all figured out. One final question. Should I interconnect all of my 3560s and then string all of my 2960s off of those 3560s?

I would run dual, trunked links between 2 of the 3560's and set L3 redundant routing on the Vlan Interfaces (Like HSRP) and if either failed, the other switch would take over (This would be like your backbone/core.

I would use the 3rd 3560 for switching only but for possibly servers. Run dual conections (1 to each L3 3560). STP will stop it from looping.

Then single or dual home your remaining switches (depending on user's importance) back to the L3 3560's. You might want to make 1 of the L3 3560's a VTP Server, then the rest VTP clients and put them in the same VTP Domain.

This is how I would set it up....

Thank you so much for your reply. This is exactly what I was looking to do. So the only part I still have a question on is when you say to use the 3rd 3560 for switching only (you mean just use it like a 2960?). Then all of my remaining 2960s just run dual links back to either of my two trunked 3560s? Do all of these 2960s need a link to both 3560s? Is there a graphical way we could explain this to each other? Thanks again, you have helped me with exactly what I was looking for.

Yes, the 3rd 3560 just like the 2960's ..no L3 routing, leave that to the 2 main 3560's.

If you want the 2960's to have High availabilty / redundancy then I would run 2 links (1 to each 3560) if possible.

2nd choice (If you don't have the wiring or fiber between closets) then 1 link back each(half to sw1, half to sw2)

3rd choice is daisy chain them (no more than 6 with default spanning-tree configuration though.